DVI to HDMI converters and Vis versa any difference ?

[Helllo]

DVI to HDMI converters and Vis versa any difference ?

Just want to know if i get a TV with DVI and or HDMI only, if i get a
converter would their be any difference will my HD Movie play work
just as good and give me HD movies on my TV ?

I know their are no HD players or Blueray ones to test this but just
like to know how much of a difference DVI and HDMI is ?

becuase i know their will be DVI and HDMI only devices just would like
to know what my options are.

Thanks.